and they mentioned that starting from 2017, we can use Web hooks to implement similar functionalities as in Remote Event Receviers. but from my reading seems web hooks can not support Synchronous events (such as adding, editting & deleting). so i have these Two questions:-

is there a way i can force my web hooks to support Synchronous events? or this can not be achieved?

if the answer for the first question is NO (Web-hooks do not support Synchronous events), then if inside my SharePoint online lists, i want to cancel the adding and editing events inside my code, then the only way i can do so is to use Remote Event Receivers? is this correct?